Aggressive advances in electronic device technology, such as for defense and space applications, have created an urgent need for revolutionary thermal management solutions to effectively spread and carry heat dissipated by integrated circuit (IC) chips and multi-chip modules (MCMs). Some conventional thermal solutions use copper alloy heat spreaders, which draw heat away from integrated circuit chips and multi-chip modules and spread the heat over a larger area. However, these thermal solutions are often limited by the thermal conductivity (200 W/mK) and thermal expansion coefficient (TEC) mismatch of the copper alloy heat spreaders. Also, the lack of flexibility of the thermal substrate can limit innovative packaging configurations.
In other conventional thermal solutions, heat pipes are used to help transport heat generated by electronic systems. By their nature, heat pipes are well suited for both long distance transport and for heat flux transformation (accepting a high heat flux at the source and ejecting it as a low heat flux at some other location, usually with a minimal change in temperature). Most heat pipes used for electronics cooling are made with copper as the envelope material and water as the working fluid. Heat pipes are often made in both cylindrical tube shapes and in low profile cuboids called vapor chamber heat pipes. Heat pipes have a much higher effective thermal conductivity for long-distance transport (compared to copper), but heat pipers are less effective in short-distance transport due to wick thermal resistance. Although the wick thermal resistance can be reduced by using a thinner wick layer or a smaller pore size, this typically leads to reduced capacity to handle heat flux (such as critical heat flux) due to increased liquid flow resistance in the wick capillary.